Lake Winnipeg Watershed Annual Lake Chlorophyll-a Database 1984-2023

The zipped archive contains a comprehensive catalog of input geospatial data and scripts with which a 40-year (1984-2023) time series of annual median Chl-a estimates were generated for 27,313 lakes ≥ 10 ha in the Lake Winnipeg watershed. The dataset includes three folders. In the first folder (“Input Lake Data”), geospatial databases showing lake boundaries in the Lake Winnipeg watershed as vector polygon feature layers are provided as input data for subsequent scripts. The geodatabases include the “raw” (i.e., unfiltered and unprocessed) lake boundaries (Input Lake Data.gdb) and the results of filtering (Filtered Lakes.gdb) and processing to generate the geodatabase used as input data for the scripts (Buffered Filtered Lakes.gdb). The lake boundaries were extracted from the open-source HydroLAKES database (Messager et al., 2016). The folder also contains a geodatabase showing the boundary of the Lake Winnipeg watershed for reference purposes (Lake Winnipeg Watershed.gdb). The second folder (“Annual Chl-a Estimation”) contains (1) Google Earth Engine code in Word (Google Earth Engine Annual Lake Chl-a Estimation Code.docx) and text (Google Earth Engine Annual Lake Chl-a Estimation Code.txt) formats for generating natural log-transformed annual median Chl-a estimates in μg L-1 for all lakes in the input geodatabase for all years from 1984 to 2023 and (2) an R script (Chl-a Time Series Merger.R) and exporting the results in a comprehensive Excel workbook organized by unique lake IDs in rows and annual median lake Chl-a estimates in columns. The third folder (“Output Lake Chl-a Data”) contains the annual median lake Chl-a estimate output from input data and codes as described in the first and second folders in an Excel workbook (Annual median lake Chl-a and trophic states.xlsb). The workbook includes worksheets showing (1) the direct output (i.e., natural log-transformed annual median lake Chl-a in μg L-1), (2) back-transformed (i.e., unscaled) annual median lake Chl-a in μg L-1, and (3) annual trophic state classifications derived from the annual median lake Chl-a estimates per Carlson (1977) (i.e., Chl-a < 2.6 μg L-1 = oligotrophic, < 7.3 μg L-1 = mesotrophic, < 56 μg L-1 = eutrophic, and ≥ 56 μg L-1 = hypereutrophic). Also provided in the third folder are two geodatabases for spatially visualizing the annual median lake Chl-a estimates (Annual lake median Chl-a.gdb and Annual lake trophic state.gdb); both geodatabases were created by joining worksheets in the workbook (i.e., back-transformed annual median lake Chl-a in μg L-1 and annual trophic state classifications, respectively) to the filtered lake vector polygon feature database in the first folder (Filtered Lakes.gdb). The data contents of each folder are described in ReadMe text files.